Ground Rod For Residence ?

Hello:

Was just wondering about this a bit. Live in the Boston area, in a typical Colonial built about 30 yrs ago.

Have the "standard" 220 V line coming into the house from the street line Appears to be 3 conductors, the 2 phases and the neutral.

My question is that I keep reading about houses needing, and the NEC requiring, a ground (or grounding) rod right outside the house.

Don't seem to have one.

Is an actual ground rod required ? Where would it be ?

If not, why not ?

Thanks, Bob

Hello:

Was just wondering about this a bit. Live in the Boston area, in a typical Colonial built about 30 yrs ago.

Have the "standard" 220 V line coming into the house from the street line Appears to be 3 conductors, the 2 phases and the neutral.

My question is that I keep reading about houses needing, and the NEC requiring, a ground (or grounding) rod right outside the house.

Don't seem to have one.

Is an actual ground rod required ? Where would it be ?

If not, why not ?

Thanks, Bob

You are grounded to the water pipe coming in the house. As long as the water company doesn't replace it with plastic you are fine. The new code requires another electrode beside the pipe for that reason.

Yes.

Usually not far from the main service entrance. You should see an uninsulated conductor leading from the ground rod into the main service panel.

Ah, there's the question now isn't it? In the past, it was acceptable to use the incoming cold water pipe for a ground. The reasoning was that iron/copper (even old lead) piping made an excellent ground by interconnecting with all the other water pipes in town. So you might find an uninsulated conductor running from your main service panel over to a cold water pipe in the basement/crawlspace.

But times change. With the advent of PVC and plastic water meters and other things, using the cold water pipe as the sole grounding rod is no longer permitted. So if you have any major work done, you will have to also put in a new ground rod to bring it up to current code.

daestrom

A ground "rod" isn't the only viable ground. The "UFER" ground is supplanting the ground rod as the method of choice in most Western states. A UFER is either a copper conductor poured in it's own concrete, or in the foundation concrete of the building. Often a piece of re-bar is turned up from the foundation under the service for this purpose. Check this link out, if you're interested.

This is how we do it in SW Florida.

Nice pictures! Ed

I always pictured copper wire coming out of the footing. Rebar up makes the thing look indestructable. Presume green is anti-rust and doesn't impair conductivity?

The link above from Long Tom seems to say you can't use Ufer alone without a rod. Can't you use Ufer alone without anything else?

I just looked at info that included Ufer. Original test was over 18 years with resistance range from 2.1 to 4.8 ohms average 3.6 ohms. Would think these would replace rods.

There was also info from a Mike Holt video from Orlando where he drove a

10' rod with a water table about 3' down, connected 120V and got a current of about 1.5A (implies 80 ohms). He added lengths do a depth of 50' where the current was 14A (implies 8.6 ohms). Any idea why such dismal results? Oddity of Florida?

bud--

They just shoot it green so it won't get confused with the dowel rods and get the cell in the block poured solid. That is a water based paint they wash off before the connection in the last picture is made. The hole in the block gets a mud ring at stucco and a stainless blank cover so it stays accessible.

The rest of those vertical #5s go up through the block, get tied to two #5s across the top 2 courses and all of that gets poured solid. This ends up being a virtual faraday cage.

The sany soil makes "Ground" in Florida is a fairly ambigous thing and the difference between 2 buildings can spike 35v or more on a Dranitz monitor. The Ufer just insures an equipotential grid in the building you are in. When they build a radio tower or a toll booth they go to extraordinary lengths to get a good ground. Typically a tool booth gets a Ufer, a ground ring around the whole plaza and several 40 foot rods along the ring. A radio tower gets all that plus buried radials. It may still not be "ground" but it is a stable reference.

Haqve you ever watch the shows about the University of Central Floirida/ Florida Powere & Light project to study lightning? They shoot rockets up into charged clouds to induce a controlled strike and analyse the result. It does somewhat debunk the idea that a buried power line is safe trom ligntning. The lightning is still making glass out of sand 5 or 6 feet down. Still plenty of energy to spike a power line.

Whether or not it will damage a buried power line depends on a number of factors, including shielding and grounding. What is most important is the potential difference between the "live" and the "grounded" conductors or objects. A low ground resistance certainly is beneficial and it doesn't require an excessively large conductor to handle the very short duration current without overheating.

Given all that, the flow of lightning current in the ground is very often not predictable.

A grounded ring in the foundation and top of the wall? Sounds like great lightning protection. Steel reinforced concrete block tied to the foundation sounds like a bomb shelter but is probably for hurricanes?

If the water table is high why don't disolved minerals give high conductivity?

bud--

If it is where the rockets trail fine wire I saw an hour program. IIRC the program had interesting information on the electrical findings; seems like science programs now are dumbded down and a lot less frequent. Looked like it would be real interesting to watch the tests. From inside a good shelter.

bud--

Yup that is the coastal wind code. It is even more stringent in south Dade county and the Keys.

We saw the value when Wilma came and some folks who didn't get their tie beams poured lost their walls. When you see the pile of rubble that used to be a block wall it will conmvince you wind is powerful stuff. Once you get steel and concrete in there you got ya something.